Posted By
Litwr
on 2016-01-01
14:27:22
|  Re: A mathematical demo
+4/NTSC is a bit faster with the screen off than +4/PAL. I can't see point to edit line 120 - it just prevents to set NTSC mode for the NTSC hardware.  There is also no reason to set slower PAL mode for the NTSC hardware. The change of mode also requires the adequate change for the timer calculation. So the only result 2.41 sec (+4/NTSC with screen blank) is reliable. This result is a bit surprising. +4/PAL with screen blank and no NTSC gives 2.4 - this is a bit faster. IMHO this result is caused by more frequent NTSC video interrupts that consume more CPU ticks than PAL.
Amstrad CPC is slow down by the video system to the actual 3.2 MHz instead of 4 MHz of the system quartz. Unlike Commodore Amstrad can' disable its video system. BTW my code for z80 is not the fastest. I am testing the program which is at least 20% faster. So it looks like that 6502 is only 60-80% faster than z80 for 16-bit arithmetic.
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